PVA films are made of PVA resins which are thermoplastic and yet water-soluble. The PVA films are significantly different in various film properties and texture than hydrophobic films such as polyethylene terephthalate films and polyolefin films which are generally used as packaging films.
Conventionally, chemical agent portion packages (unit packages) have been proposed which each include a bag formed from a PVA resin film and a chemical agent such as an agricultural chemical or a detergent contained in the bag, and take advantage of the water solubility of the PVA resin. The unit packages are used in a wide variety of applications.
Known examples of the PVA resin film to be used for the water-soluble unit packages in such applications include: a water-soluble film (see, for example, PTL 1) which comprises 100 parts by weight of a PVA, 5 to 30 parts by weight of a plasticizer, 1 to 10 parts by weight of starch and 0.01 to 2 parts by weight of a surfactant; and a water-soluble film (see, for example, PTL 2) which comprises 100 parts by weight of an anionic group-modified PVA resin (A) having a 4 wt. % aqueous solution viscosity of 10 to 35 mPa·s as measured at 20° C., an average saponification degree of 80.0 to 99.9 mol % and an anionic group modification degree of 1 to 10 mol %, 20 to 50 parts by weight of a plasticizer (B), 2 to 30 parts by weight of a filler (C) and 0.01 to 2.5 parts by weight of a surfactant (D).